<?php
/**
 * CodeIgniter
 *
 * An open source application development framework for PHP
 *
 * This content is released under the MIT License (MIT)
 *
 * Copyright (c) 2014 - 2016, British Columbia Institute of Technology
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 *
 * @package    CodeIgniter
 * @author    EllisLab Dev Team
 * @copyright    Copyright (c) 2008 - 2014, EllisLab, Inc. (https://ellislab.com/)
 * @copyright    Copyright (c) 2014 - 2016, British Columbia Institute of Technology (http://bcit.ca/)
 * @license    http://opensource.org/licenses/MIT	MIT License
 * @link    https://codeigniter.com
 * @since    Version 1.3.0
 * @filesource
 */
defined('BASEPATH') OR exit('No direct script access allowed');

/**
 * MS SQL Database Adapter Class
 *
 * Note: _DB is an extender class that the app controller
 * creates dynamically based on whether the query builder
 * class is being used or not.
 *
 * @package        CodeIgniter
 * @subpackage    Drivers
 * @category    Database
 * @author        EllisLab Dev Team
 * @link        https://codeigniter.com/user_guide/database/
 */
class CI_DB_mssql_driver extends CI_DB
{

    /**
     * Database driver
     *
     * @var    string
     */
    public $dbdriver = 'mssql';

    // --------------------------------------------------------------------

    /**
     * ORDER BY random keyword
     *
     * @var    array
     */
    protected $_random_keyword = array('NEWID()', 'RAND(%d)');

    /**
     * Quoted identifier flag
     *
     * Whether to use SQL-92 standard quoted identifier
     * (double quotes) or brackets for identifier escaping.
     *
     * @var    bool
     */
    protected $_quoted_identifier = TRUE;

    // --------------------------------------------------------------------

    /**
     * Class constructor
     *
     * Appends the port number to the hostname, if needed.
     *
     * @param    array $params
     * @return    void
     */
    public function __construct($params)
    {
        parent::__construct($params);

        if (!empty($this->port)) {
            $this->hostname .= (DIRECTORY_SEPARATOR === '\\' ? ',' : ':') . $this->port;
        }
    }

    // --------------------------------------------------------------------

    /**
     * Non-persistent database connection
     *
     * @param    bool $persistent
     * @return    resource
     */
    public function db_connect($persistent = FALSE)
    {
        $this->conn_id = ($persistent)
            ? mssql_pconnect($this->hostname, $this->username, $this->password)
            : mssql_connect($this->hostname, $this->username, $this->password);

        if (!$this->conn_id) {
            return FALSE;
        }

        // ----------------------------------------------------------------

        // Select the DB... assuming a database name is specified in the config file
        if ($this->database !== '' && !$this->db_select()) {
            log_message('error', 'Unable to select database: ' . $this->database);

            return ($this->db_debug === TRUE)
                ? $this->display_error('db_unable_to_select', $this->database)
                : FALSE;
        }

        // Determine how identifiers are escaped
        $query = $this->query('SELECT CASE WHEN (@@OPTIONS | 256) = @@OPTIONS THEN 1 ELSE 0 END AS qi');
        $query = $query->row_array();
        $this->_quoted_identifier = empty($query) ? FALSE : (bool)$query['qi'];
        $this->_escape_char = ($this->_quoted_identifier) ? '"' : array('[', ']');

        return $this->conn_id;
    }

    // --------------------------------------------------------------------

    /**
     * Select the database
     *
     * @param    string $database
     * @return    bool
     */
    public function db_select($database = '')
    {
        if ($database === '') {
            $database = $this->database;
        }

        // Note: Escaping is required in the event that the DB name
        // contains reserved characters.
        if (mssql_select_db('[' . $database . ']', $this->conn_id)) {
            $this->database = $database;
            $this->data_cache = array();
            return TRUE;
        }

        return FALSE;
    }

    // --------------------------------------------------------------------

    /**
     * Affected Rows
     *
     * @return    int
     */
    public function affected_rows()
    {
        return mssql_rows_affected($this->conn_id);
    }

    // --------------------------------------------------------------------

    /**
     * Insert ID
     *
     * Returns the last id created in the Identity column.
     *
     * @return    string
     */
    public function insert_id()
    {
        $query = version_compare($this->version(), '8', '>=')
            ? 'SELECT SCOPE_IDENTITY() AS last_id'
            : 'SELECT @@IDENTITY AS last_id';

        $query = $this->query($query);
        $query = $query->row();
        return $query->last_id;
    }

    // --------------------------------------------------------------------

    /**
     * Returns an object with field data
     *
     * @param    string $table
     * @return    array
     */
    public function field_data($table)
    {
        $sql = 'SELECT COLUMN_NAME, DATA_TYPE, CHARACTER_MAXIMUM_LENGTH, NUMERIC_PRECISION, COLUMN_DEFAULT
			FROM INFORMATION_SCHEMA.Columns
			WHERE UPPER(TABLE_NAME) = ' . $this->escape(strtoupper($table));

        if (($query = $this->query($sql)) === FALSE) {
            return FALSE;
        }
        $query = $query->result_object();

        $retval = array();
        for ($i = 0, $c = count($query); $i < $c; $i++) {
            $retval[$i] = new stdClass();
            $retval[$i]->name = $query[$i]->COLUMN_NAME;
            $retval[$i]->type = $query[$i]->DATA_TYPE;
            $retval[$i]->max_length = ($query[$i]->CHARACTER_MAXIMUM_LENGTH > 0) ? $query[$i]->CHARACTER_MAXIMUM_LENGTH : $query[$i]->NUMERIC_PRECISION;
            $retval[$i]->default = $query[$i]->COLUMN_DEFAULT;
        }

        return $retval;
    }

    // --------------------------------------------------------------------

    /**
     * Error
     *
     * Returns an array containing code and message of the last
     * database error that has occured.
     *
     * @return    array
     */
    public function error()
    {
        // We need this because the error info is discarded by the
        // server the first time you request it, and query() already
        // calls error() once for logging purposes when a query fails.
        static $error = array('code' => 0, 'message' => NULL);

        $message = mssql_get_last_message();
        if (!empty($message)) {
            $error['code'] = $this->query('SELECT @@ERROR AS code')->row()->code;
            $error['message'] = $message;
        }

        return $error;
    }

    // --------------------------------------------------------------------

    /**
     * Execute the query
     *
     * @param    string $sql an SQL query
     * @return    mixed    resource if rows are returned, bool otherwise
     */
    protected function _execute($sql)
    {
        return mssql_query($sql, $this->conn_id);
    }

    // --------------------------------------------------------------------

    /**
     * Begin Transaction
     *
     * @return    bool
     */
    protected function _trans_begin()
    {
        return $this->simple_query('BEGIN TRAN');
    }

    // --------------------------------------------------------------------

    /**
     * Commit Transaction
     *
     * @return    bool
     */
    protected function _trans_commit()
    {
        return $this->simple_query('COMMIT TRAN');
    }

    // --------------------------------------------------------------------

    /**
     * Rollback Transaction
     *
     * @return    bool
     */
    protected function _trans_rollback()
    {
        return $this->simple_query('ROLLBACK TRAN');
    }

    // --------------------------------------------------------------------

    /**
     * Set client character set
     *
     * @param    string $charset
     * @return    bool
     */
    protected function _db_set_charset($charset)
    {
        return (ini_set('mssql.charset', $charset) !== FALSE);
    }

    // --------------------------------------------------------------------

    /**
     * Version number query string
     *
     * @return    string
     */
    protected function _version()
    {
        return "SELECT SERVERPROPERTY('ProductVersion') AS ver";
    }

    // --------------------------------------------------------------------

    /**
     * List table query
     *
     * Generates a platform-specific query string so that the table names can be fetched
     *
     * @param    bool $prefix_limit
     * @return    string
     */
    protected function _list_tables($prefix_limit = FALSE)
    {
        $sql = 'SELECT ' . $this->escape_identifiers('name')
            . ' FROM ' . $this->escape_identifiers('sysobjects')
            . ' WHERE ' . $this->escape_identifiers('type') . " = 'U'";

        if ($prefix_limit !== FALSE && $this->dbprefix !== '') {
            $sql .= ' AND ' . $this->escape_identifiers('name') . " LIKE '" . $this->escape_like_str($this->dbprefix) . "%' "
                . sprintf($this->_like_escape_str, $this->_like_escape_chr);
        }

        return $sql . ' ORDER BY ' . $this->escape_identifiers('name');
    }

    // --------------------------------------------------------------------

    /**
     * List column query
     *
     * Generates a platform-specific query string so that the column names can be fetched
     *
     * @param    string $table
     * @return    string
     */
    protected function _list_columns($table = '')
    {
        return 'SELECT COLUMN_NAME
			FROM INFORMATION_SCHEMA.Columns
			WHERE UPPER(TABLE_NAME) = ' . $this->escape(strtoupper($table));
    }

    // --------------------------------------------------------------------

    /**
     * Update statement
     *
     * Generates a platform-specific update string from the supplied data
     *
     * @param    string $table
     * @param    array $values
     * @return    string
     */
    protected function _update($table, $values)
    {
        $this->qb_limit = FALSE;
        $this->qb_orderby = array();
        return parent::_update($table, $values);
    }

    // --------------------------------------------------------------------

    /**
     * Truncate statement
     *
     * Generates a platform-specific truncate string from the supplied data
     *
     * If the database does not support the TRUNCATE statement,
     * then this method maps to 'DELETE FROM table'
     *
     * @param    string $table
     * @return    string
     */
    protected function _truncate($table)
    {
        return 'TRUNCATE TABLE ' . $table;
    }

    // --------------------------------------------------------------------

    /**
     * Delete statement
     *
     * Generates a platform-specific delete string from the supplied data
     *
     * @param    string $table
     * @return    string
     */
    protected function _delete($table)
    {
        if ($this->qb_limit) {
            return 'WITH ci_delete AS (SELECT TOP ' . $this->qb_limit . ' * FROM ' . $table . $this->_compile_wh('qb_where') . ') DELETE FROM ci_delete';
        }

        return parent::_delete($table);
    }

    // --------------------------------------------------------------------

    /**
     * LIMIT
     *
     * Generates a platform-specific LIMIT clause
     *
     * @param    string $sql SQL Query
     * @return    string
     */
    protected function _limit($sql)
    {
        $limit = $this->qb_offset + $this->qb_limit;

        // As of SQL Server 2005 (9.0.*) ROW_NUMBER() is supported,
        // however an ORDER BY clause is required for it to work
        if (version_compare($this->version(), '9', '>=') && $this->qb_offset && !empty($this->qb_orderby)) {
            $orderby = $this->_compile_order_by();

            // We have to strip the ORDER BY clause
            $sql = trim(substr($sql, 0, strrpos($sql, $orderby)));

            // Get the fields to select from our subquery, so that we can avoid CI_rownum appearing in the actual results
            if (count($this->qb_select) === 0) {
                $select = '*'; // Inevitable
            } else {
                // Use only field names and their aliases, everything else is out of our scope.
                $select = array();
                $field_regexp = ($this->_quoted_identifier)
                    ? '("[^\"]+")' : '(\[[^\]]+\])';
                for ($i = 0, $c = count($this->qb_select); $i < $c; $i++) {
                    $select[] = preg_match('/(?:\s|\.)' . $field_regexp . '$/i', $this->qb_select[$i], $m)
                        ? $m[1] : $this->qb_select[$i];
                }
                $select = implode(', ', $select);
            }

            return 'SELECT ' . $select . " FROM (\n\n"
            . preg_replace('/^(SELECT( DISTINCT)?)/i', '\\1 ROW_NUMBER() OVER(' . trim($orderby) . ') AS ' . $this->escape_identifiers('CI_rownum') . ', ', $sql)
            . "\n\n) " . $this->escape_identifiers('CI_subquery')
            . "\nWHERE " . $this->escape_identifiers('CI_rownum') . ' BETWEEN ' . ($this->qb_offset + 1) . ' AND ' . $limit;
        }

        return preg_replace('/(^\SELECT (DISTINCT)?)/i', '\\1 TOP ' . $limit . ' ', $sql);
    }

    // --------------------------------------------------------------------

    /**
     * Insert batch statement
     *
     * Generates a platform-specific insert string from the supplied data.
     *
     * @param    string $table Table name
     * @param    array $keys INSERT keys
     * @param    array $values INSERT values
     * @return    string|bool
     */
    protected function _insert_batch($table, $keys, $values)
    {
        // Multiple-value inserts are only supported as of SQL Server 2008
        if (version_compare($this->version(), '10', '>=')) {
            return parent::_insert_batch($table, $keys, $values);
        }

        return ($this->db->db_debug) ? $this->db->display_error('db_unsupported_feature') : FALSE;
    }

    // --------------------------------------------------------------------

    /**
     * Close DB Connection
     *
     * @return    void
     */
    protected function _close()
    {
        mssql_close($this->conn_id);
    }

}
